It is known to use Dual-Tone, Multi-Frequency (DTMF) signaling over telephone lines. DTMF signaling operates by sending and detecting different combinations of two individual tones, which can be generated by a simple circuit in a telephone set. This type of signaling has been used for dialing and switching purposes, as well as for end-user control applications, such as Interactive Voice Response (IVR) systems. More recently, telephone conversations generated with DTMF-based telephone sets are also being sent over packet-switched networks, such as the Internet.